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1. Shanasa Rahel et al Int. Journal of Engineering Research and Applications
ISSN : 2248-9622, Vol. 3, Issue 6, Nov-Dec 2013, pp.2181-2185
RESEARCH ARTICLE
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OPEN ACCESS
Implementation and Analysis of Wimax Module under Ns2 with
Varying Mobility Model
Shanasa Rahel¹, Deepali Shukla²
1
M.E. (Electronics and Communication)
²Asst. Prof. Dept of E&C, MITM, Indore
Abstract
The network simulator 2 (ns-2) is a popular and powerful simulation tool for the simulation of packet-switched
networks, which provides substantial support for simulation of TCP, routing, and MAC protocols over wired
and wireless networks, such as wireless LANs, mobile ad hoc networks (MANETs), and satellite
communications, etc, and is widely used in both academia and industry. Although many protocol modules have
been implemented in the ns-2, the IEEE 802.16 broadband wireless access networks (BWANs) or WiMAX
module has not been contributed yet. Thus, in this paper, we present our detailed design and implementation of
the WiMAX module based on the IEEE 802.16 standard with the point-to-multipoint (PMP) mode for the ns-2.
The implemented module comprises fundamental functions of the service-specific convergence sublayer (CS),
the MAC common part sublayer (CPS), and the PHY layer. A simple call admission control (CAC) mechanism
and the scheduler are also included in this module.
I.
Introduction
The IEEE 802.16 standard forms the basis
of Worldwide Interoperability for Microwave Access
(WiMAX). It was developed by the WiMAX Forum
with the objective of providing high speed data
transfers over the air. The WiMAX Forum is an
industry-led, non-profit organization that certifies
and promotes the compatibility and interoperability
of broadband wireless products based upon IEEE
Standard 802.16 [1]. WiMAX has its origin in the
computer industry and is an alternative to Third
Generation Partnership Project (3GPP) and
technologies like High Speed Packet Access (HSPA)
and Long Term Evolution (LTE).
The most popular network simulator used
by the academia and industry is the network
simulator 2 (ns-2) [11], which has become the de
facto standards for the simulation of packet-switched
networks. Specifically, more and more published
wireless network studies and investigations use ns-2
to evaluate and verify their work. Although there still
another force investigates the IEEE 802.16-based
simulator [8], this simulator is not public. The ns-2 is
roughly composed of various traffic models,
transport-layer protocols, network-layer protocols,
and medium access control (MAC) layer protocols,
etc. These components enable ns-2 to simulate
different types of networks and their topologies.
Researchers can benefit from these preliminary tests
on their investigation and find out the drawbacks of
their new design in efficient way.
Until today, as the best knowledge of the
authors, no WiMAX/IEEE 802.16 module has been
contributed to ns-2. Due to these reasons, we design
and implement the WiMAX module for ns-2. The
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developed WiMAX module is focused on MAC
protocol development and inherited from the original
MAC class in ns-2. This module is based on IEEE
802.16 point-to-multipoint (PMP) mode, which
means that one BS can serve multiple subscriber
stations (SSs) concurrently. We choose the
orthogonal frequency-division multiple access
(OFDMA) scheme for the physical (PHY) layer.
Based on the OFDMA PHY specifications, it has
been of major interest for both wireless applications
due to its high date rate transmission capability and
its robustness to multipath delay spread [9].
The IEEE 802.16 standard defines the
specifications related to the service-specific
convergence sublayer (CS), the MAC common part
sublayer (CPS), the security sublayer, and the PHY
layer. The MAC management messages, such as
downlink/ uplink map (DL-MAP/UL-MAP),
downlink/uplink channel descriptor (DCD/UCD),
ranging request/response (RNGREQ/ RNG-RSP),
and so forth are implemented following the 802.16
standard to operate the WiMAX networks. All
operations between the base station (BS) and
subscriber stations (SSs) over a superframe interval
follow the compulsory procedures of the 802.16
standard.
II.
An Overview of IEEE 802.16
Standards
The section briefly summarizes the
operations of MAC and PHY layers in the IEEE
802.16 standard. Fig. 1 illustrates the architecture of
IEEE 802.16. The CS provides any transformation or
mapping of external network data that is received
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2. Shanasa Rahel et al Int. Journal of Engineering Research and Applications
ISSN : 2248-9622, Vol. 3, Issue 6, Nov-Dec 2013, pp.2181-2185
through the CS service access point (SAP) and
converts them into MAC service data units (MSDUs)
received by the MAC layer through the MAC SAP.
This sublayer includes classifying external network
SDUs and associating them to the proper MAC
service flow identifier (SFID) and connection ID
(CID). In addition, it may also include the payload
header suppression (PHS) function.
The MAC CPS provides the core MAC
functionality of system access, bandwidth allocation,
scheduling, contention mechanism, connection
establishment, and connection maintenance. It
receives data from various CSs through the MAC
SAP, which is classified to particular MAC
connections. The IEEE 802.16-2004 standard
supports four quality-of-service scheduling types:
unsolicited grant service (UGS) for the constant bit
rate (CBR) service, real-time polling service (rtPS)
for the variable bit rate (VBR) service, non-real-time
polling service (nrtPS) for non-real-time VBR, and
best effort service (BE) for service with no rate or
delay requirements. In 802.16e standard, there is an
additional service type called extended real-time
polling service (ertPS) for voice over IP (VoIP)
service with silence suppression.
These quality-of-service (QoS) classes are
associated with certain predefined sets of QoSrelated service flow parameters, and the MAC
scheduler supports the appropriate data handling
mechanisms for data transport according to each
QoS classes. The upper-layer protocol data units
(PDUs) are inserted into different levels of queues
with an assigned CID in the MAC layer after the
SFID-CID mapping. These data packets in these
queues are treated as MSDUs and then will be
fragmented or packed into various sizes according to
the MAC scheduling operations. They will be
processed by a selective repeat automatic repeat
request (ARQ) block mechanism if the ARQ-enabled
function is on.
For the UL traffic, each SS should range to
the BS before entering the system. During the initial
ranging period, the SS will request to be served in
the DL via the particular burst profile by transmitting
its choice of DL interval usage code (DIUC) to the
BS. Afterwards, the BS will command the SS to use
a particular uplink burst profile with the allocated
UL interval usage code (UIUC) with the grant of SS
in UL-MAP messages. The DL-MAP and UL-MAP
contain the channel ID and the MAP information
elements (IEs) which describes the PHY
specification mapping in the UL and DL
respectively. They are based on the different PHY
specifications, such as single carrier (SC), single
carrier access (SCa), OFDM, and OFDMA. The
burst profile includes the DIUC, UIUC, and the typelength-value (TLV) encoded information. The TLV
encoded information will notify the PHY layer of the
modulation type, FEC code type, and encoding
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parameters. The MAC data payload is packed by
these encoding type.
The PHY layer requires equal radio link
control (RLC), which is the capability of the PHY
layer to transit from one burst profile to another. The
RLC begins with the periodic BS broadcasting of the
burst profiles which have been chosen for the
downlink or the uplink connections. After the initial
determination of downlink and uplink burst profiles
between the BS and a particular SS, RLC continues
to monitor and control the burst profiles. The SS can
range with the RNGREQ message to request a
change in the downlink burst profile. The channel
measurements report request (REPREQ) message
will be used by a BS to request signal-to-noise ratio
(SNR) channel measurements reports. The channel
measurement report response (REP-RSP) message is
used by the SS to respond the channel measurements
listed in the received REP-REQ.
The IEEE 802.16 uses the frame-based
transmission architecture where the frame length is
variable. Each frame is called a superframe and is
divided into two subframes: the DL subframe and
the UL subframe. In this paper, we are focusing the
frame structure of the OFDMA-PHY in time division
duplex (TDD) mode. A DL subframe consists of DL
subframe prefix to specify the modulation and
coding (in PHY mode), the length of the first DL
burst, and the broadcasted MAC control messages,
e.g., the downlink channel descriptor (DCD) and the
uplink channel descriptor (UCD). Both of them
define the characteristics of the physical channels by
comprising the detail information of the DL burst
profile and the UL burst profile.
Although IEEE 802.16 defines the
connection signaling (connection requests and
responses) between SS and BS, itdoes not define the
admission control process. All packets from the
application layer are classified by the connection
classifier based on the CID and are forwarded to the
appropriate queue. At the SS, the scheduler will
retrieve the packets from the queues and transmit
them to the network in the appropriate time slots as
defined by the UL-MAP sent by the BS. The ULMAP is determined by the scheduler module based
on the BW-request messages. These messages report
the current queue size of each connection in SS.
The IEEE 802.16 NS-2 Modules:
The developed 802.16-based WiMAX
module named as the Mac802 16 class is in
accordance with the specifications of the IEEE
802.16-2004 standard [1] and based on the ns-2
version 2.29 [11]. All modules are designed by using
object oriented programming language C++ and
modeled as several classes. The relationship between
the WiMAX module and legacy ns-2 modules is
based on the original network component stack of
the ns-2 as shown in Fig 2. It illustrates the type of
objects for the traffic generating agent (TGA), the
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3. Shanasa Rahel et al Int. Journal of Engineering Research and Applications
ISSN : 2248-9622, Vol. 3, Issue 6, Nov-Dec 2013, pp.2181-2185
link layer (LL), the interface queue (IFQ), the
designed MAC layer (WiMAX module), and the
PHY layer (Channel).
First, the TGA is considered simply as an
application level traffic generator that generates
VoIP, MPEG, FTP, HTTP traffic, and so on. These
traffic are classified into five different types of
service, the UGS, rtPS, ertPS, nrtPS, and BE, each
with its own priority. All packets will be transferred
to different types of priority queues according to
their service types by using CS layer SFID-CID
mapping mechanism. The data packets in these
queues are treated as MSDUs and will be selected to
pass into the WiMAX module in a round robin
manner.
While the WiMAX module in the SS
receives the MSDUs from the Queue object, the
MAC management component will initiate the
ranging process to enter the WiMAX system or to
transmit the MSDUs according to the scheduled time
obtained from UL-MAP. Once the process has been
successfully finished in the MAC layer, the Network
Interface will add a propagation delay and broadcast
in the air interface.
Simulation environment:
Simulation Tool
No.Of Nodes
IEEE Standard
BS
Mobility Model
Antenna Model
Mobility Speed
Routing Protocol
Simulation Area
Simulation Time
III.
NS-2
40
802.16
1
Random Way Point
Omni Directional
20m/sec,250m/sec
AODV,DSR,DSDV
2 Km
200 sec.
Results & Analysis
Wimax with low mobility Model:
Parameter
AODV
DSR
DSDV
Delay(in ms)
146.73
413.15
139.44
Throughput(in
kbps)
539.41
413.15
659.26
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End to End Delay Analysis: From Below Graphs in
Fig1 and 2 it is clear that when node moves very
rapidly than the delay is low as compare to the delay
when the speed of nodes are slow.
500
400
300
200
100
0
AODV
DSR
DSDV
Figure-1
126
124
122
120
118
116
114
112
110
108
Delay(in ms)
AODV
DSR
DSDV
Figure-2
Throughput Analysis: In terms of throughput it is
clear from below figure 3 & 4 that the wimax
module with high mobility in fig-3 shows better Data
transmission known as throughput in kbps. In low
speed model throughput is less as compare with
high speed model shown in fig-4.
700
600
PDR (in %)
96.19
96.16
93.06
500
400
Throughput(in kbps)
300
Wimax with low mobility Model:
200
Parameter
AODV
DSR
DSDV
Delay(in ms)
122.14
124.73
114.34
Throughput(in
666.76
651.69
680.68
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0
Figure-3
kbps)
PDR (in %)
100
98.45
99.32
96.34
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4. Shanasa Rahel et al Int. Journal of Engineering Research and Applications
ISSN : 2248-9622, Vol. 3, Issue 6, Nov-Dec 2013, pp.2181-2185
www.ijera.com
References:
[1]
700
600
500
400
Throughput(in kbps)
300
200
100
0
AODV
DSR
DSDV
Figure-4
Packet Delivery Ratio Analysis: In terms of packet
delivery ratio the wimax module with high mobility
in figure 5 shows better performance than that of
with low mobility model in figure-6 in our case we
have taken low mobility scenario as 25m/sec and
high mobility scenario as 250 m/sec
99.5
99
98.5
98
97.5
97
96.5
96
95.5
95
94.5
PDR (in %)
AODV
DSR
DSDV
Figure-5
97
96
95
94
PDR (in %)
93
92
91
AODV
DSR
DSDV
Figure-6
Conclusion: We have implemented Firstly Wimax
Module under Ns-2 Simulator and then analyzed its
performance under various routing protocols. From
above results it is clear that when in a wimax
scenario nodes move rapidly than the overall
performance of network is good in terms of PDR and
Throughput as Compare to the scenario having slow
speed of node movement.
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NETWORK
SIMULATOR
(ns2).
http://www.isi.edu/nsnam/ns/.
Marc
Geris'
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UCB/LBNL/VINT Network Simulator "ns"
www.ijera.com
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